1 /*
2 * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciField.hpp"
27 #include "ci/ciInstanceKlass.hpp"
28 #include "ci/ciUtilities.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "gc_interface/collectedHeap.inline.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "memory/universe.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "oops/oop.inline2.hpp"
35 #include "runtime/fieldDescriptor.hpp"
36
37 // ciField
38 //
39 // This class represents the result of a field lookup in the VM.
40 // The lookup may not succeed, in which case the information in
41 // the ciField will be incomplete.
42
43 // The ciObjectFactory cannot create circular data structures in one query.
44 // To avoid vicious circularities, we initialize ciField::_type to NULL
45 // for reference types and derive it lazily from the ciField::_signature.
46 // Primitive types are eagerly initialized, and basic layout queries
47 // can succeed without initialization, using only the BasicType of the field.
48
49 // Notes on bootstrapping and shared CI objects: A field is shared if and
50 // only if it is (a) non-static and (b) declared by a shared instance klass.
51 // This allows non-static field lists to be cached on shared types.
52 // Because the _type field is lazily initialized, however, there is a
53 // special restriction that a shared field cannot cache an unshared type.
54 // This puts a small performance penalty on shared fields with unshared
55 // types, such as StackTraceElement[] Throwable.stackTrace.
56 // (Throwable is shared because ClassCastException is shared, but
57 // StackTraceElement is not presently shared.)
58
59 // It is not a vicious circularity for a ciField to recursively create
60 // the ciSymbols necessary to represent its name and signature.
61 // Therefore, these items are created eagerly, and the name and signature
62 // of a shared field are themselves shared symbols. This somewhat
63 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
64 // with all of the additional 43 being uninteresting shared ciSymbols.
65 // This adds at most one step to the binary search, an amount which
66 // decreases for complex compilation tasks.
67
68 // ------------------------------------------------------------------
69 // ciField::ciField
70 ciField::ciField(ciInstanceKlass* klass, int index): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
71 ASSERT_IN_VM;
72 CompilerThread *thread = CompilerThread::current();
73
74 assert(ciObjectFactory::is_initialized(), "not a shared field");
75
76 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constan-pool");
77
78 constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
79
80 // Get the field's name, signature, and type.
81 Symbol* name = cpool->name_ref_at(index);
82 _name = ciEnv::current(thread)->get_symbol(name);
83
84 int nt_index = cpool->name_and_type_ref_index_at(index);
85 int sig_index = cpool->signature_ref_index_at(nt_index);
86 Symbol* signature = cpool->symbol_at(sig_index);
87 _signature = ciEnv::current(thread)->get_symbol(signature);
88
89 BasicType field_type = FieldType::basic_type(signature);
90
91 // If the field is a pointer type, get the klass of the
92 // field.
93 if (field_type == T_OBJECT || field_type == T_ARRAY) {
94 bool ignore;
95 // This is not really a class reference; the index always refers to the
96 // field's type signature, as a symbol. Linkage checks do not apply.
97 _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
98 } else {
99 _type = ciType::make(field_type);
100 }
101
102 _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
103
104 // Get the field's declared holder.
105 //
106 // Note: we actually create a ciInstanceKlass for this klass,
107 // even though we may not need to.
108 int holder_index = cpool->klass_ref_index_at(index);
109 bool holder_is_accessible;
110 ciInstanceKlass* declared_holder =
111 ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
112 holder_is_accessible,
113 klass)->as_instance_klass();
114
115 // The declared holder of this field may not have been loaded.
116 // Bail out with partial field information.
117 if (!holder_is_accessible) {
118 // _type has already been set.
119 // The default values for _flags and _constant_value will suffice.
120 // We need values for _holder, _offset, and _is_constant,
121 _holder = declared_holder;
122 _offset = -1;
123 _is_constant = false;
124 return;
125 }
126
127 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
128
129 // Perform the field lookup.
130 fieldDescriptor field_desc;
131 Klass* canonical_holder =
132 loaded_decl_holder->find_field(name, signature, &field_desc);
133 if (canonical_holder == NULL) {
134 // Field lookup failed. Will be detected by will_link.
135 _holder = declared_holder;
136 _offset = -1;
137 _is_constant = false;
138 return;
139 }
140
141 assert(canonical_holder == field_desc.field_holder(), "just checking");
142 initialize_from(&field_desc);
143 }
144
145 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
146 ASSERT_IN_VM;
147
148 // Get the field's name, signature, and type.
149 ciEnv* env = CURRENT_ENV;
150 _name = env->get_symbol(fd->name());
151 _signature = env->get_symbol(fd->signature());
152
153 BasicType field_type = fd->field_type();
154
155 // If the field is a pointer type, get the klass of the
156 // field.
157 if (field_type == T_OBJECT || field_type == T_ARRAY) {
158 _type = NULL; // must call compute_type on first access
159 } else {
160 _type = ciType::make(field_type);
161 }
162
163 initialize_from(fd);
164
165 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
166 assert(is_shared() || ciObjectFactory::is_initialized(),
167 "bootstrap classes must not create & cache unshared fields");
168 }
169
170 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
171 if (holder == NULL)
172 return false;
173 if (holder->name() == ciSymbol::java_lang_System())
174 // Never trust strangely unstable finals: System.out, etc.
175 return false;
176 // Even if general trusting is disabled, trust system-built closures in these packages.
177 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
178 return true;
179 return TrustFinalNonStaticFields;
180 }
181
182 void ciField::initialize_from(fieldDescriptor* fd) {
183 // Get the flags, offset, and canonical holder of the field.
184 _flags = ciFlags(fd->access_flags());
185 _offset = fd->offset();
186 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
187
188 // Check to see if the field is constant.
189 bool is_final = this->is_final();
190 bool is_stable = FoldStableValues && this->is_stable();
191 if (_holder->is_initialized() && (is_final || is_stable)) {
192 if (!this->is_static()) {
193 // A field can be constant if it's a final static field or if
194 // it's a final non-static field of a trusted class (classes in
195 // java.lang.invoke and sun.invoke packages and subpackages).
196 if (is_stable || trust_final_non_static_fields(_holder)) {
197 _is_constant = true;
198 return;
199 }
200 _is_constant = false;
201 return;
202 }
203
204 // This field just may be constant. The only cases where it will
205 // not be constant are:
206 //
207 // 1. The field holds a non-perm-space oop. The field is, strictly
208 // speaking, constant but we cannot embed non-perm-space oops into
209 // generated code. For the time being we need to consider the
210 // field to be not constant.
211 // 2. The field is a *special* static&final field whose value
212 // may change. The three examples are java.lang.System.in,
213 // java.lang.System.out, and java.lang.System.err.
214
215 KlassHandle k = _holder->get_Klass();
216 assert( SystemDictionary::System_klass() != NULL, "Check once per vm");
217 if( k() == SystemDictionary::System_klass() ) {
218 // Check offsets for case 2: System.in, System.out, or System.err
219 if( _offset == java_lang_System::in_offset_in_bytes() ||
220 _offset == java_lang_System::out_offset_in_bytes() ||
221 _offset == java_lang_System::err_offset_in_bytes() ) {
222 _is_constant = false;
223 return;
224 }
225 }
226
227 Handle mirror = k->java_mirror();
228
229 switch(type()->basic_type()) {
230 case T_BYTE:
231 _constant_value = ciConstant(type()->basic_type(), mirror->byte_field(_offset));
232 break;
233 case T_CHAR:
234 _constant_value = ciConstant(type()->basic_type(), mirror->char_field(_offset));
235 break;
236 case T_SHORT:
237 _constant_value = ciConstant(type()->basic_type(), mirror->short_field(_offset));
238 break;
239 case T_BOOLEAN:
240 _constant_value = ciConstant(type()->basic_type(), mirror->bool_field(_offset));
241 break;
242 case T_INT:
243 _constant_value = ciConstant(type()->basic_type(), mirror->int_field(_offset));
244 break;
245 case T_FLOAT:
246 _constant_value = ciConstant(mirror->float_field(_offset));
247 break;
248 case T_DOUBLE:
249 _constant_value = ciConstant(mirror->double_field(_offset));
250 break;
251 case T_LONG:
252 _constant_value = ciConstant(mirror->long_field(_offset));
253 break;
254 case T_OBJECT:
255 case T_ARRAY:
256 {
257 oop o = mirror->obj_field(_offset);
258
259 // A field will be "constant" if it is known always to be
260 // a non-null reference to an instance of a particular class,
261 // or to a particular array. This can happen even if the instance
262 // or array is not perm. In such a case, an "unloaded" ciArray
263 // or ciInstance is created. The compiler may be able to use
264 // information about the object's class (which is exact) or length.
265
266 if (o == NULL) {
267 _constant_value = ciConstant(type()->basic_type(), ciNullObject::make());
268 } else {
269 _constant_value = ciConstant(type()->basic_type(), CURRENT_ENV->get_object(o));
270 assert(_constant_value.as_object() == CURRENT_ENV->get_object(o), "check interning");
271 }
272 }
273 }
274 if (is_stable && _constant_value.is_null_or_zero()) {
275 // It is not a constant after all; treat it as uninitialized.
276 _is_constant = false;
277 } else {
278 _is_constant = true;
279 }
280 } else {
281 _is_constant = false;
282 }
283 }
284
285 // ------------------------------------------------------------------
286 // ciField::compute_type
287 //
288 // Lazily compute the type, if it is an instance klass.
289 ciType* ciField::compute_type() {
290 GUARDED_VM_ENTRY(return compute_type_impl();)
291 }
292
293 ciType* ciField::compute_type_impl() {
294 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
295 if (!type->is_primitive_type() && is_shared()) {
296 // We must not cache a pointer to an unshared type, in a shared field.
297 bool type_is_also_shared = false;
298 if (type->is_type_array_klass()) {
299 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
300 } else if (type->is_instance_klass()) {
301 type_is_also_shared = type->as_instance_klass()->is_shared();
302 } else {
303 // Currently there is no 'shared' query for array types.
304 type_is_also_shared = !ciObjectFactory::is_initialized();
305 }
306 if (!type_is_also_shared)
307 return type; // Bummer.
308 }
309 _type = type;
310 return type;
311 }
312
313
314 // ------------------------------------------------------------------
315 // ciField::will_link
316 //
317 // Can a specific access to this field be made without causing
318 // link errors?
319 bool ciField::will_link(ciInstanceKlass* accessing_klass,
320 Bytecodes::Code bc) {
321 VM_ENTRY_MARK;
322 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
323 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
324 "unexpected bytecode");
325
326 if (_offset == -1) {
327 // at creation we couldn't link to our holder so we need to
328 // maintain that stance, otherwise there's no safe way to use this
329 // ciField.
330 return false;
331 }
332
333 // Check for static/nonstatic mismatch
334 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
335 if (is_static != this->is_static()) {
336 return false;
337 }
338
339 // Get and put can have different accessibility rules
340 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
341 if (is_put) {
342 if (_known_to_link_with_put == accessing_klass) {
343 return true;
344 }
345 } else {
346 if (_known_to_link_with_get == accessing_klass) {
347 return true;
348 }
349 }
350
351 fieldDescriptor result;
352 LinkResolver::resolve_field(result, _holder->get_instanceKlass(),
353 _name->get_symbol(), _signature->get_symbol(),
354 accessing_klass->get_Klass(), bc, true, false,
355 KILL_COMPILE_ON_FATAL_(false));
356
357 // update the hit-cache, unless there is a problem with memory scoping:
358 if (accessing_klass->is_shared() || !is_shared()) {
359 if (is_put) {
360 _known_to_link_with_put = accessing_klass;
361 } else {
362 _known_to_link_with_get = accessing_klass;
363 }
364 }
365
366 return true;
367 }
368
369 // ------------------------------------------------------------------
370 // ciField::print
371 void ciField::print() {
372 tty->print("<ciField name=");
373 _holder->print_name();
374 tty->print(".");
375 _name->print_symbol();
376 tty->print(" signature=");
377 _signature->print_symbol();
378 tty->print(" offset=%d type=", _offset);
379 if (_type != NULL)
380 _type->print_name();
381 else
382 tty->print("(reference)");
383 tty->print(" flags=%04x", flags().as_int());
384 tty->print(" is_constant=%s", bool_to_str(_is_constant));
385 if (_is_constant && is_static()) {
386 tty->print(" constant_value=");
387 _constant_value.print();
388 }
389 tty->print(">");
390 }
391
392 // ------------------------------------------------------------------
393 // ciField::print_name_on
394 //
395 // Print the name of this field
396 void ciField::print_name_on(outputStream* st) {
397 name()->print_symbol_on(st);
398 }